The present invention relates to a surgical instrument used in an endoscopic surgical operation.
Endoscopic surgical operations are conducted extensively these days. In these operations, endoscopic images that are displayed on a monitor are observed as treatment is carried out. An instrument used in the treatment has an axis that is long enough for extracorporeal manipulation.
In general, the instrument of this type is passed through a cylindrical member, called a trocar, which connects the interior of a patient's body and the outside. Since the trocar is fixed in its entrance position, in this case, the instrument and an organism as an object of treatment are not always in desirable relative positions. Thus, manipulating the instrument requires technical skill of a user.
The manipulation of the instrument is difficult in the case where the instrument is held extending in the direction of the tangent to the plane of an organism as a to-be-treated object or where the viewing direction of an endoscope is close to the axial direction of the instrument, in particular.
In excising only a mucomembranous structure of the stomach or intestine under observation through an endoscope, as a specific example, a medical solution is locally injected into a submucosa by means of a injection needle. If the injection needle is located so that its central axis extends in the direction of the tangent to the plane of the target mucomembranous structure, in doing this, it is difficult to thrust the needle deep into the mucomembranous structure. In this case, therefore, the medical solution cannot be easily injected to an appropriate depth in the mucomembranous structure.
In the case of biopsy, moreover, an organism is partially excised and recovered by means of a cup- shaped forceps, called a bioptome, having a sharp edge. If the plane of the organism and the central axis of the forceps are substantially parallel to each other, also in this case, the organism cannot be excised satisfactorily.
Described in Jpn. Pat. Appln. KOKAI Publication Nos. 5-253178, 5-253179 and 5-253298 are instruments that have been developed to solve these problems. These instruments are provided with a bending device for bending a injection needle on the handling side, whereby the needle can be thrust squarely into a target organism.
Described in Jpn. Pat. Appln. KOKAI Publication No. 5-261062, moreover, is an instrument in-which the tip portion of a injection needle is formed of a shape-memory alloy, and needling is facilitated by using means for remotely heating the needle tip portion. According to an arrangement disclosed in Jpn. Pat. Appln. KOKAI Publication No. 8-332189, furthermore, an area near the distal end portion of a bioptome is bendable in any desired direction.
In conducting cholangiography in the course of laparoscopic cholecystectomy, another difficulty is found in inserting a catheter to inject a contrast medium via the cystic duct. In a typical method of contrast medium injection for this technique, a soft tub called a contrast catheter is held by means of a forceps as it is guided to and inserted into an incision region in the cystic duct. During this treatment, the central axis of the catheter is not always in line with the extending direction of the cystic duct. Even after the catheter tube is inserted into the incision region with success, moreover, it is liable to be caught by a valve in the cystic duct. Thus, the catheter cannot be inserted deep into the duct.
Described in U.S. Pat. No. 5,167,645 is an instrument in which a bent portion is attached to the distal end of a bile-duct catheter in order to solve these problems. According to an arrangement described in U.S. Pat. No. 5,389,090, furthermore, the efficiency of insertion is improved by using a hollow tube that is previously made highly susceptible to bending.
In any of the cases described above, the central axis of the distal end portion is inclined at a certain angle to that of the instrument, in order to improve the direction of approach of the instrument to the target organism.
According to the aforementioned conventional injection needle with the bendable tip, however, the degree of its curvature cannot be changed although its curved shape is variable. In the case where an endoscope and the needle are arranged substantially coaxially, therefore, the shaft of the needle extends in the viewing direction of the endoscope, so that the range of the endoscope may possibly be intercepted by the shaft. In this case, it is necessary to change the course of the needle by bending the needle, and in addition, to change or increase the size of the bendable portion, thereby enabling the obstructive needle shaft to escape from the range of the endoscope. Since the curvature of the conventional needle is unchangeable, however, the impedimental needle shaft cannot be allowed to get away from the range.
In locally injecting the wall of a narrow duct, in contrast with this, the instrument cannot be caused squarely to approach a mucomembranous structure unless its bendable portion is reduced in size.
In the case of the catheter with its distal end easily bendable for cholangiography, its curved shape cannot be changed freely. This arrangement facilitates the insertion only when the catheter and the target tubular organism are in specific or restricted relative positions. If the catheter and the organism are not in these specific relative positions, however, the efficiency of insertion of the catheter cannot be improved. Thus, the catheter with the bendable distal end cannot be highly insertable under various conditions.
In inserting a catheter into the cystic duct, in general, the catheter is easily caught by a spiral fold (valve) in the duct, so that it cannot be inserted deep into the duct. In this case, the distal end of the catheter must be directed so that its curved shape can be frequently changed to clear the fold. In order to pass the spiral fold, moreover, the bendable portion is expected to have a measure of stiffness (rigidity). Since this requirement cannot be fulfilled according to the prior art described above, however, inserting the catheter into the cystic duct is a hard task. According to this arrangement, furthermore, the curved shape of the distal end of the catheter cannot be changed, so that a trocar having an unreasonably large diameter should be used to receive the bendable portion of the catheter. Thus, a large hole must be bored in the patient's body.